Researchers have found that a specific gene could determine West Africans' susceptibility to tuberculosis. They say this could help explain why only a small fraction of people exposed to the bacteria develop serious disease.

Tuberculosis (TB) infects almost a third of the world's population but only 10 per cent of affected people develop symptoms.

Previous studies have shown that a single gene controls resistance and susceptibility to TB in mice. Now, a team led by Adrian Hill of the UK-based Wellcome Trust has studied the corresponding human gene, SP110. They investigated whether it is associated with TB symptoms in populations from West Africa.

The team collected DNA from family members of over 400 TB patients from The Gambia, Guinea-Conakry and Guinea-Bissau.

Different ethnic groups have subtly different versions of the gene, so using family members of TB patients minimised these differences making it easier to show an association between SP110 and the disease.

Of the 27 genetic variations found, three versions of SP110 were associated with TB symptoms.

The gene's precise function in the disease is unknown but it is thought to control the death of infected cells.

The new research was published yesterday (19 June) in the journal Proceedings of the National Academy of Sciences. Hill says the work could provide important clues on how to design new therapies and ways to prevent TB.

Reference: Proceedings of the National Academy of Sciencesdoi: 10.1073_pnas.0603340103 (2006)